Question

The photo electric work function of a metal is 2.2 eV when light of wavelength 5000Å is incident on it, maximum velocity of ejected e is 3.2 x 105 m/s. Calculate Planck’s constant​

Answer 1

Given that,

Work function = 2.2 eV

Wave length $\lambda= 5000\ \AA$

Velocity $v= 3.2\times10^{5}\ m/s$

We need to calculate the planck's constant

Using formula of work function

$\phi=\dfrac{hc}{\lambda}$

$h=\dfrac{\lambda\times\phi}{c}$

Where, h = planck constant

c = speed of light

$\lambda$ =wavelength

Put the value into formula

$h=\dfrac{5000\times10^{-10}\times2.2\times1.6\times10^{-19}}{3\times10^{8}}$

$h=5.866\times10^{-34}\ J/s$

Hence, The planck's constant is $5.866\times10^{-34}\ J/s$